Getting Ruby syntax errors in a simple example/exercise - ruby

Question

I am newbie to ruby. Below is my code where I am trying to find a value which has value true and put it into values. But getting error
possible_values =
[
'ABC',
'DEF',
'GHI',
'JKL',
'MNO',
'PQR'
]
options = {
"environment"=>"dev",
"status"=>"valid",
"abc"=>true,
"def"=>true,
"ghi"=>false,
"jkl"=>false
}
options['values'] = []
possible_values.each do |val|
options['values'] << val if options[val.downcase]
options.delete("val")
end
puts "values: #{options['values'}"
Error: can't convert String into Integer (TypeError)
Desired Output:
options = [
"environment"=>"dev",
"status"=>"valid",
"values"=>["ABC", "DEF"]
]

Answer 1

Three bugs:
Your puts line is missing a ]:
puts "values: #{options['values'}"
# ^ should be here
You want to remove the options key after processing it, but you're always removing "val" instead:
options.delete("val")
# ^ ^ extra quotes making this a "val" String
Again, you want to remove the options key after processing. The possible_values are all uppercase, and won't match the corresponding keys in options for deletion without a downcase. Taking #2 and #3 together, what you want is: options.delete(val.downcase)
After fixing all three of these, this is the contents of options:
{"environment" => "dev", "status" => "valid", "values" => ["ABC", "DEF"]}
which seems to be what you wanted

Answer 2

I see you wish to mutate (modify) options, as opposed to returning a separate hash, leaving options unchanged.
I would be inclined to write the code as follows, in part to facilitate the testing of true_keys and options (below), after true_keys has been computed.
true_keys = options.keys.each_with_object([]) do |k,arr|
case options[k]
when true
arr << k.upcase
options.delete(k)
when false
options.delete(k)
end
end
#=> ["ABC", "DEF"]
We now have:
options
#=> {"environment"=>"dev", "status"=>"valid"}
Notice that we cannot write
true_keys = options.each_key.each_with_object([]) do |k,arr|...
or
true_keys = options.each_with_object([]) do |(k,v),arr|...
because that would remove elements of options whilst interating over it, a no-no. That is not a problem when iterating over options.keys.
One more step:
options.tap { |h| h['values'] = true_keys & possible_values }
#=> {"environment"=>"dev", "status"=>"valid", "values"=>["ABC", "DEF"]}
See Object#tap.
Just checking:
options
#=> {"environment"=>"dev", "status"=>"valid", "values"=>["ABC", "DEF"]}
One could alternatively write
options.update('values'=>true_keys & possible_values)
#=> {"environment"=>"dev", "status"=>"valid", "values"=>["ABC", "DEF"]}
See Hash#update (a.k.a. merge!).
If options and possible_values were large it would be sensible to convert possible_values to a set as an initial step, as set lookups are much faster than array lookups, the latter requiring a linear search. This only effects the tap (or update) operation.
require 'set'
possible_values_set = possible_values.to_set
#=> #<Set: {"ABC", "DEF", "GHI", "JKL", "MNO", "PQR"}>
Then with
true_keys
#=> ["ABC", "DEF"]
the tap expression would become:
options.tap do |h|
h['values'] = true_keys.select { |k| possible_values_set.include?(k) }
end
#=> {"environment"=>"dev", "status"=>"valid", "values"=>["ABC", "DEF"]}